Many types of input devices are presently available for performing operations in a computing system, such as buttons or keys, mice, trackballs, joysticks, touch sensor panels, touch screens and the like. Touch screens, in particular, are becoming increasingly popular because of their ease and versatility of operation as well as their declining price. Touch screens can include a touch sensor panel, which can be a clear panel with a touch-sensitive surface, and a display device positioned partially or fully behind the panel so that the touch-sensitive surface can cover at least a portion of the viewable area of the display device. The display device can include technologies such as liquid crystal displays (LCDs), organic light emitting diode (OLED) displays, etc. OLEDs, for example, can provide a flat or flexible display in a relatively thin package that can be suitable for use in a variety of portable electronic devices. In addition, OLED displays can display brighter and more vibrant images in a thinner and lighter package compared to LCD displays, making them suitable for use in compact portable electronic devices.
Advantages of OLED displays over other types of displays make integrating OLED displays into portable electronic devices attractive. Integrating the OLED display and touch screen into a single device can include fabricating the OLED stack on a glass or plastic substrate, forming the touch sensors on the OLED stack, and electrically coupling the touch sensors and transistors for the OLED stack using routing traces and one or more metallization layers. Alternatively, the OLED stack and the touch screen can be fabricated separately and then adhered together using a conductive paste. However, both techniques can include high temperature or high pressure processes that can damage the OLED stack. Furthermore, stacking the touch sensors and any routing circuitry for the touch sensors on the OLED stack can lead to portable electronic devices with unacceptable thicknesses. Additionally, formation of the OLED stack on a glass or plastic substrate can lead to poor manufacturing yields, high process variations, and poor transistor/wiring performance.